Employer Stock in Your 401(k): The Hidden Concentration Risk

There are a handful of 401(k) plan features that regulators, academics, and practicing fiduciaries have been quietly uneasy about for twenty-plus years. Near the top of that list: employer stock held inside the plan.

It’s not that employer stock is illegal — it isn’t. Many thoughtful plans hold some. The issue is concentration: the percentage of plan assets sitting in a single security issued by the same company that signs the employees’ paychecks. When that percentage gets large, the plan has stopped being a diversified retirement vehicle and has started being a leveraged bet on one employer’s continued success.

This post is about what that risk actually looks like, where it shows up on a Form 5500, and what ERISA asks of fiduciaries who find themselves running a plan with meaningful employer-stock exposure.

What “concentration risk” actually means here

In portfolio language, concentration risk is the exposure that comes from putting too much of your money in too few places. For a 401(k) participant, employer stock is uniquely concentrated in a way diversified mutual funds are not.

Worse, it’s correlated with something most participants don’t think of as a financial asset: their job. If the company that employs you runs into trouble, two things tend to happen at once. Your paycheck becomes less secure, and the stock inside your 401(k) falls. Finance people call this covariance risk — the risk of your human capital and your financial capital moving in the same direction at the worst possible moment.

A diversified S&P 500 fund doesn’t do this. Employer stock does.

The canonical example (and why it still matters)

The textbook case is Enron, which in 2001 went from a Fortune 10 company to bankrupt in a matter of months. At the time, Enron’s 401(k) plan held roughly 62% of its assets in Enron stock — partly employee-elected, partly because employer matching contributions were made in stock that couldn’t be diversified until employees reached a certain age. When the stock went to zero, employees didn’t just lose their jobs. Many lost a meaningful portion of their retirement savings in the same calendar quarter.

Enron prompted the Pension Protection Act of 2006, which added ERISA §204(j) — the diversification rights provision — giving participants the right to diversify out of publicly traded employer securities held in their 401(k) account after reaching certain service thresholds. That law closed one structural trap, but the underlying financial risk didn’t go away.

More recent examples don’t need naming to make the point. Every few years, a company that was considered a safe long-term holding gets into trouble — accounting, regulatory, product, competitive — and participants who were overweight employer stock in their 401(k) absorb a disproportionate share of the pain. The details change; the pattern doesn’t.

What ERISA asks of the fiduciary

The key statutory language lives in ERISA §404(a)(1)(C) — the “prudent diversification” duty. It says fiduciaries must diversify plan investments “so as to minimize the risk of large losses, unless under the circumstances it is clearly prudent not to do so.”

Two things about that language are worth sitting with.

First, it’s a default rule in favor of diversification, not against it. A fiduciary who lets a plan become concentrated in employer stock has to be prepared to articulate, with evidence, why it was clearly prudent not to diversify. That’s a high bar.

Second, the law recognizes limited exceptions. ERISA §407(d)(3) creates a carve-out for “eligible individual account plans” — specifically, 401(k) plans and ESOPs designed to hold employer securities. For these plans, the 10% cap on employer securities that applies to defined-benefit plans doesn’t apply. But the diversification duty under §404(a)(1)(C) still does, and courts have generally read the two provisions together: the §407(d)(3) carve-out permits employer stock above 10%; it doesn’t require any particular amount, and it doesn’t override the prudent-diversification duty in all circumstances.

In plain English: a fiduciary doesn’t have to cap employer stock at 10%, but a fiduciary also can’t hide behind that carve-out if the concentration becomes imprudent. The Moench line of cases and the Supreme Court’s 2014 Fifth Third Bancorp v. Dudenhoeffer decision framed the current test — fiduciaries are not entitled to a presumption of prudence when holding employer stock, and must plausibly weigh the risks like any other investment.

Research from the Investment Company Institute shows that employer-stock holdings in 401(k) plans have been declining for two decades, largely because fiduciaries and plan sponsors have grown cautious about the exposure. Diversification is the direction of travel.

Where it shows up on Form 5500

For any plan filing Schedule H (generally, plans with 100+ participants), employer-stock concentration is visible in line 1c(13) — Employer securities of the Assets and Liabilities section. That line reports the dollar value of securities issued by the plan sponsor held inside the plan.

Divide line 1c(13) by line 1c (total plan assets), and you have your concentration ratio.

There’s no statutory threshold at which this becomes “too much,” but in practice:

• Under ~5% — generally a legacy position or an incidental holding. Unremarkable.
• 5–15% — worth watching, particularly if the plan isn’t actively rebalancing.
• 15–30% — concentrated enough that fiduciary review, employee communications, and diversification policy should be in writing.
• Above ~30% — material concentration. Diversification mechanics, covariance risk, and participant education need active attention.

For plans with a KSOP structure (a 401(k) combined with an ESOP), these ratios will naturally run higher because the ESOP side is designed to hold employer stock. The fiduciary analysis is different for a KSOP, but the core duty to diversify where prudent still applies.

What sponsors can do

If you’re a plan sponsor with meaningful employer-stock exposure in your 401(k), the fiduciary playbook is well-established and entirely within reach:

• Document the diversification policy. Written rebalancing rules, limits on new employer-stock contributions, and participant-election guardrails all help show that the fiduciary is actively managing the exposure.
• Honor diversification rights. Publicly traded employer stock held in a 401(k) must, under ERISA §204(j), be freely diversifiable once participants meet the service requirement. The plan should make this easy, not bury it in paperwork.
• Communicate the risk to participants. The DOL publishes participant-facing materials on diversification that are helpful to distribute alongside enrollment materials.
• Benchmark against peers. Most mid-sized plans now hold well under 5% in employer stock by design. A plan with substantially more deserves a thoughtful, documented reason why.
• Run the concentration ratio annually. Line 1c(13) ÷ line 1c on Schedule H is a one-minute calculation. Knowing the number is the minimum standard.

This is not advice to sell anything. A well-run employer can be a fine long-term investment, and some of the most successful 401(k) plans in America hold meaningful employer stock without harming participants. The fiduciary question isn’t whether employer stock is good or bad; it’s whether the concentration is being managed thoughtfully and whether participants have real tools to diversify if they want to.

Want us to check your plan?

If you’re not sure what percentage of your plan’s assets sits in employer securities, run your plan through our free Plan Lookup tool. We pull line 1c(13) directly from your most recent Schedule H filing, calculate the concentration ratio, and flag anything meaningfully above peer norms — along with the other red flags we check for on every plan. If your plan has something worth discussing, we’ll connect you with a licensed Texas-based 401(k) advisor for a free 15-minute review. No cost, no pitch if there’s nothing to fix. If you want to go deeper first, our guide on how to read your Form 5500 walks through Schedule H line by line.